The present invention relates to a plant cultivating device, in particular, a plant cultivating device which enables plant cultivation by efficient use of floor space in an expensive building erected in an urban district.
A proper amount of nutrients and proper atmospheric conditions such as carbon-dioxide (co.sub.2), water, temperature and humidity, etc. are needed in order to effectively nurture plants. However, it is often difficult to obtain all of these at one time. The ground needs to be prepared for nurturing plants. However, it is not easy to acquire space or ground for cultivating plants in urban districts.
In order to solve such a problem, the present applicant previously proposed a method or an apparatus in which solar rays were focused by a lense or the like and guided into an optical conductor and then further guided through the optical conductor onto a plant cultivating device which was installed in an optional desired place for receiving light energy for plants. Furthermore the present applicant has proposed a plant cultivating device in which artificial light rays were employed in addition to solar rays. (Refer to Japanese Patent Application No. 58-119866.)
The plant performs a photosynthesis through the use of light energy given it and delivers or transmits nutritious substances produced by the action of the photosynthesis to its trunk, fruits, etc. Such delivery of transportation can be more effectively carried out when there is no light; there is sufficient oxygen; and there is a low ambient temperature. Therefore, in order to nurture plants, more effectively, it is necessary to cause photosynthesis to occur and then nutrious substances are transmitted to the limbs, trunk, and fruit of the plant. In order to effectively cause photosynthesis to occur and for the subsequent transmission of nutrients to the limbs, trunk and fruits of plant to take place, periods of brightness and darkness must be alternated at predetermined intervals.
Furthermore, in the case of nurturing plants, it may be preferable to supply light rays to the plant intermittently (several .mu.s to several ms) instead of continuously. Specifically, the photosynthesis consists of a brightness reaction and a darkness reaction, and intensified light rays are given to the plant during the time period of a brightness reaction while no light rays or rather weakened light rays are given during the time period of a darkness reaction. In such a manner, the growth of the plant is enhanced.
When using a movable light source device, the utilization area of light energy can be increased compared with the use of a fixed light source. Namely, in the case of employing a light source of the same capacity, the plant can be cultivated over a wider area. In addition to that, the shadowed portion created by the leaves of the plant changes every moment in accordance with the afore-mentioned movement of the light source device, so that the brightness reaction and the darkness reaction are effectively alternated. In such a manner, growth of the plant can be much more effectively promoted.
Furthermore, in order to nurture the plant effectively, it is necessary to give it a proper amount of nutritious substances, light rays, water, carbon-dioxide, temperature, and humidity. The plant cultivating tub has to be hermetically-sealed in order to supply carbon-dioxide. By employing such a construction, the plant cultivating tub can be supplied with air containing carbon-dioxide.
Furthermore, in order to cultivate plants more effectively, they need to be provided with a period of brightness and a period of darkness corresponding to day time and night time. Those periods have to be in an order of hours. The brightness period represents the time period for performing a photosynthesis while the darkness period represents the time period for performing a delivery or transportation of nutritious substances from the leaves, to the fruits, and to the trunk. During the brightness period, carbon-dioxide is needed for performing the photosynthesis. On the contrary, oxygen is needed for breathing during the darkness period. Therefore, it may be preferable to supply carbon-dioxide of a comparatively high and adequate temperature and an adequate humidity during the brightness period and to supply oxygen of a comparatively low temperature during the darkness period.